The present invention relates to a planar high-frequency antenna formed by radiating elements for high-frequency signals. The antenna includes at least two conducting plates provided with oppositely-arranged openings. Disposed between each pair of successive plates there is a thin dielectric sheet supporting an array of strip conductors forming suspended-substrate mircostrip lines with these plates. The ends of the strip conductors extend into cavities formed by the openings and serve as radiating elements.
A planar high-frequency antenna comprising an array of such elements is disclosed in French Patent Applications Nos. 81 08 780 (corresponding to U.S. Pat. No. 4,486,758), No. 82 04 252 (corresponding to U.S. Pat. No. 4,527,165) and No. 82 18 700 (corresponding to allowed U.S. Patent Application Ser. No. 548,263 filed on Nov. 3, 1983).
More specifically, an arrangement is described in FIG. 3 of French patent application No. 82 18 700 which enables the positioning of the strip conductors of the transmission lines constituting the supply networks of the antenna. Each of these networks of high-frequency lines in constituted by a printed circuit provided on a thin dielectric sheet serving as a substrate and inserted between two metal plates or metal-plated dielectrics. Each network is arranged such that the ends of the strip conductors of the lines extend into cavities formed by openings in the plates between which the dielectric sheet is disposed, in such manner as to couple the lines and the cavities. These networks of strip conductors are positioned in a corresponding network of slots provided in each of the plates, which form with these strip conductors coaxial transmission lines of the "suspended-substrate-line" (SSL) type.
Arrangements of this type have two disadvantages. On the one hand the manufacturing tolerances of the slots and the tolerances for positioning the strip conductors in the slots are very small. On the other hand, the losses in the lines increase, to a first approximation, in an inverse ratio to the width of the slots.